The present invention relates to electronic image processing wherein data represents three dimensional objects.
Computer graphics systems are known in which the positions of points in three dimensional space may be stored, usually in the form of Cartesian coordinates. Such systems may be used, for example, in computer aided design, graphic art, computer animation or flight simulation. In all of these systems the information is presented to an observer as a two dimensional projection on a television - type monitor or similar device.
In known systems the three dimensional data is stored as points and the object may be displayed by connecting the points by lines producing a wire frame model. Systems capable of manipulating these wire frame models in real-time have been known for some time, the real-time manipulation of solid objects being much more difficult.
A system for simulating three dimensional deformations to a planar surface is disclosed in European patent application 211,345, having specific application to displaying faces and body shapes. The deformations are normal to the planar surface. The surfaces produced are defined with respect to the planar surface and are not true three dimensional surfaces.
A computer aided design system in which positional and colour information both form part of the three dimensional data is disclosed in an article "Now 3-D CAD images can be moved in real time" published in the US journal "Electronics" on 7 Aug. 1986. The article discloses an application of a Hewlett-Packard 320SRX chip which is particularly fast at rendering three dimensional point data to a two dimensional display image, a process it refers to a scan conversion. The three dimensional data comprises six fields representing x, y, z position and RGB colour. A Bresenham alogorithm is then used which takes stored point values and interpolates them to find every pixel of the two dimensional image that must be lit to draw the line.
In the known systems the emphasics is placed on minimising the three dimensional data so as to (a) reduce storage space and, (b) reduce processing required convert the data to a two dimensional image. However a problem with systems of this type is that they do not allow modification of fine detail of the three dimensional image thus restricting the efforts of artists to create realistic images which are not obviously computer generated.
In our United Kingdom Patent No. 2,119,594 (equivalent to U.S. Pat. No. 4,709,393) there is described a video processing system for picture shape manipulation which comprises frame storage means for receiving a sequence of picture point signals constituting an input picture, address means for identifying selected addresses in said storage means for the sequence of picture point signals and for storing the picture point signals at the repective identified addresses, and means for reading the picture point signals from the addresses in said storage means in a predetermined order to reproduce picture point signals representing the input picture after shape manipulation. The picture point signals constituting the input picture are received in raster order, and the selection of the addresses in the frame storage means at which the picture point signals are stored is such as to rearrange the picture point signals (relative to their raster position on input) to produce the change in shape of the picture. Upon reading the picture point signals from the store, the addresses in the store are accessed in sequence. The shape manipulation which is required may have the result that a selected address for a particular picture point signal at the input does not coincide with the address of any storage location in the frame storage means but falls between a number of adjacent storage location addresses. In that case the picture point signal is distributed proportionally to the adjacent addresses.
A selection of addresses for producing a change in the shape of a particular input picture defines the position of a matrix of points on a "skin" conforming to the desired shape, and when the addresses are used to re-arrange the input picture point signals, the corresponding picture assumes the shape of the skin. Each selection of addresses defining a particular skin is called an address map, and a store is provided for storing a variety of address maps defining shape transformations. By using a series of related shapes, a corresponding series of input pictures (which may in fact be modified repetitions of a single input picture) appear to change continuously through the series of shapes giving the effect of animation.
In our United Kingdom Patent No. 2,158,671 (equivalent U.S. patent application No. 713,028) there is described a video processing system generally similar to that refered to in the proceeding paragraph but in which operator controlled means is provided for manipulating a selection of address signals constituting an address map, to represent movement of the skin defined by the address map. Such movement may be a translation or rotation, or both, of the skin. For example assuming a particular address map defines a sphere, the operator controlled manipulation may define the sphere in successive positions as it undergoes a combined rotation and translation. To define the sphere, the address map comprises three dimensional addresses, and the addresses are projected on a notional viewing surface, before being used to identify the two dimensional addresses in the frame storage means for the input picture point signals. The rotation of the skin caused by the operator controlled means produces the effect of viewing the sphere from a changing viewpoint. The effect is therefore called "floating viewpoint".
In our British Patent No. 2,089,625 (equivalent to U.S. Pat. No. 4,633,416) there is described a video image creation system including operator controlled drafting means for designating points on a desired image, means for producing first signals representing a characteristic to be imparted to the image at said points, a store having storage locations corresponding to points on the image, processing means for producing for each point designated by said drafting means a new image signal which is a function of said first signal and of a previous image signal for the same point derived from the location in said store corresponding to the respective point, means for storing the new image signal at the location in said store corresponding to the respective point, and means for reading image signals from the store to produce an image corresponding to the stored signal. The aforesaid characteristic to be imparted to the image is usually a colour selected by the operator and the effect of the processing means is to blend this colour with any previous colour stored in the store for the particular point designated by the operator to receive the "new" colour.